Optimizing and evaluating the operational factors affecting the cyanide leaching circuit of the Aghdareh gold processing plant using a CCD model

A response surface method using a central composite design was employed to evaluate, model and optimize the influence of five main factors in the gold cyanidation process. These factors were pH, solid percentage, NaCN concentration, particle size and leaching time. A second-order equation was proposed and developed for the relationship between the gold recoveries and influential factors. The modelling results indicated that the factors influencing the degree of cyanide leaching of gold were in the order of leaching time > NaCN concentration2 > particle size > pH > NaCN concentration > leaching time2 > solid percentage × particle size > solid percentage × NaCN concentration > solid percentage. Also, we obtained a coefficient of determination (R 2 ) greater than 93%, which showed that the developed model was well fitted to the experimental data. In addition, the model equation was individually optimized by using quadratic programming to maximize gold recoveries within the experimental range. The optimum condition was found to be pH 10.11 for the solution, 36.07% for the solids content, 729.56 ppm for the NaCN concentration, 37.52 μ m for the particle size and 23.2 h for the leaching time. Under these conditions, the highest recovery of gold was achieved of approximately 91.5%.